werkzeug double-encodes redirects when processing merge_slashes

[tomprince]

from werkzeug.routing import Rule, Map

routes = Map([
    Rule("/merge/<some>/path"),
])

def get_redirect_location(path):
    try:
        routes.bind("test.host").match(path)
    except Exception as e:
        return e.get_response({}).headers['location']
    else:
        raise ValueError("no redirect")

def test_merge_slashes():
    assert get_redirect_location("/merge/%//path") == 'http://test.host/merge/%25/path'

It looks like Rule.match uses Rule.build to generate the new path here, which is already urlencoded. But then MapAdapter.match encodes the resulting path again here.

Environment:

• Python version: 3.9.5
• Werkzeug version: 2.0.1

[cAtaman]

I just opened #2193 which should fix this